Convert Acres to Square miles
1 acre is 0.001563 mi². One acre is exactly 0.0015625 square miles.
One acre is 0.0015625 square miles. To convert acres to square miles, multiply by 0.0015625; to go the other way, divide by 0.0015625 or multiply by 640. The factor is exact rather than rounded: it follows from NIST Office of Weights and Measures. Exactly 43,560 square feet — historically the land one team of oxen could plough in a day.
Factor checked against the defining standard · How we check
- Acres × 0.0015625
1 * 0.00156250.002 mi²
1 acre in every area unit
| Unit | Value | Exact factor |
|---|---|---|
| square inches | 6,272,640 sq in | × 6,272,640 |
| square feet | 43,560 sq ft | × 43,560 |
| square yards | 4,840 sq yd | × 4,840 |
| acres (as entered) | 1 ac | — |
| square meters | 4,046.856422 m² | × 4,046.8564224 |
| square millimetres | 4,046,856,422 mm² | × 4,046,856,422.4 |
| square centimetres | 40,468,564.22 cm² | × 40,468,564.224 |
| square kilometres | 0.004046856422 km² | × 0.0040468564224 |
| square miles | 0.0015625 mi² | × 0.0015625 |
| hectares | 0.4046856422 ha | × 0.40468564224 |
Factors are entered by hand from NIST Office of Weights and Measures rather than derived from a units library, so the ones that terminate are exact rather than rounded.
The same converter answers this pair however it is written: ac to sqmi is how the symbols are typed on a keyboard with no superscript on it.
How do you convert acres to square miles? The converter and the working
- 1.Take the measurement in acres.
- 2.Multiply by 0.0015625 — that is how many square miles fit in one acre.
- 3.To go back the other way, divide by 0.0015625, or multiply by 640.
Worked example: 25 acres to square miles
- Formula
- ac × 0.0015625 = mi²
- Arithmetic
- 25 × 0.0015625 = 0.04 mi²
- Answer
- 25 ac = 0.04 mi²
The factor is exact, so this figure is exact too — only the display is rounded.
Acres to square miles conversion table
| Acres | Square miles |
|---|---|
| 1 ac | 0.001563 mi² |
| 2 ac | 0.003125 mi² |
| 3 ac | 0.004688 mi² |
| 4 ac | 0.01 mi² |
| 5 ac | 0.01 mi² |
| 6 ac | 0.01 mi² |
| 7 ac | 0.01 mi² |
| 8 ac | 0.01 mi² |
| 9 ac | 0.01 mi² |
| 10 ac | 0.02 mi² |
| 12 ac | 0.02 mi² |
| 15 ac | 0.02 mi² |
| 20 ac | 0.03 mi² |
| 25 ac | 0.04 mi² |
| 50 ac | 0.08 mi² |
| 100 ac | 0.16 mi² |
| 200 ac | 0.31 mi² |
| 300 ac | 0.47 mi² |
| 500 ac | 0.78 mi² |
| 1000 ac | 1.56 mi² |
| 2000 ac | 3.13 mi² |
| 5000 ac | 7.81 mi² |
| 10000 ac | 15.63 mi² |
640 acres to the square mile, and that is by design
The US Public Land Survey divided the country into townships of 36 square miles, each square mile a section of 640 acres, each quarter-section 160 acres — the homestead. The number is round because the survey chose it, unlike the 43,560 square feet in an acre, which is inherited from a chain by a furlong. That is why rural addresses reference sections and why farm parcels come in halves and quarters of 160.
NIST Handbook 44, Appendix C — general tables of units of measurement
What is an acre?
Exactly 43,560 square feet — historically the land one team of oxen could plough in a day.
What is a square mile?
Exactly 640 acres — one section of the US Public Land Survey, the grid the Midwest is drawn on. 2.59 square kilometres, and the reason a rural address is often "section 12".
How many square miles are in an acre?
One acre is 0.0015625 square miles, exactly. Going the other way, one square mile is 640 acres. Both figures come from the same defined relation rather than from a measurement, which is why they are the same today as they were in 1959.
Every area unit here
The whole group — 10 units with their symbols and the size of each one in square meters — is on the conversion index, along with every pair it makes. The table above already gives each of them relative to an acre.
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Questions people actually ask
- How many square miles are in an acre?
- 0.0015625. Exactly 640 acres — one section of the US Public Land Survey, the grid the Midwest is drawn on. 2.59 square kilometres, and the reason a rural address is often "section 12".
- How do I convert square miles back to acres?
- Divide by 0.0015625, or multiply by 640 — they are the same operation.
Other area conversions
Square miles to acres — the same conversion the other way.